Open profile bag

ABSTRACT

A method and mechanism for preparing individual reclosable thin plastic bags with rib and groove profiles delivered in unengaged position on the finished bag, whereby said bags are made from a continuous supply of layers of film having critically shaped small rib and groove profiles on facing surfaces thereof interlocked with each other and continuously advancing the layers of film and inserting a fixed separating finger between the rib and groove profiles so as to draw them apart, maintaining the profiles in alignment by grooves which do not press the profiles flat but carefully guide them laterally, guiding the film profile layers toward each other and then immediately pressing the profile layers together with a sealing and cutting means following the finger, so that the profiles are interlocked at the location of sealing only.

BACKGROUND OF THE INVENTION

The invention relates to improvements in methods and mechanism forforming bags with interlocking continuous fasteners or zippers thereonwherein the bags are formed of a thin plastic film, and delivered withthe profiles in separated condition. The continuous material is normallyformed by an extrusion process with the profiles automaticallyinterlocked during the completion of the process, as exemplified in theteachings of U.S. Pat. No. 3,340,116, Naito.

In making bags from material of this type, the film, which is very thinon the order of several mils is formed with the fasteners normally beingintegral thereon. The profiles are interlocked so that they willmaintain their shape during the time the film is stored on a roll andhandled and shipped. Individual bags are made from the continuous rollof film by cross-cutting ends off of the layers of film and sealing theedges. The individual bags are then used by pulling the interlocked riband groove fasteners apart by flanges provided above the profiles sothat the bags can be filled and resealed.

It has been generally customary to produce such bags with a closed topand the profiles engaged, and the user must, therefore, separate the topedges of the bag by separating the rib and groove elements when the bagis to be filled. The bags have come off of the bag machine withinterlocked profiles, and separation must be made before the bags can beused and filled. This is an extra operation which consumes effort andtime. Where the bags are to be hand loaded, it normally requires about50% more time than if the bag were available with an open top with theprofiles separated. Where automatic loading is used, a method has to beprovided to open the profile in order that the bag can be delivered tothe filling station with the top open. Efforts have been made toseparate the rib and groove elements at different positions beforecross-sealing and cutting the bags, but these have been provenunsuccessful in that when the rib and grooves are separated andcross-sealing takes place, the rib and groove often do not rejoin.Either they stay apart of miss each other so that the rib is beside thegroove. If this occurs, the bag cannot thereafter be effectively sealedbecause when the rib and groove are attempted to be pressed together,the rib does not start into the groove, but presses beside it so thatthe fastener never can interlock. This has particularly become the casewith improved methods of manufacture and improved plastics which make itpossible to make the rib and grooves very small and yet sufficientlystrong to provide a good closing interlock. The smaller the rib andgroove units, the more difficult it is to join them when the seal isformed at the edge of the bag, and as above stated, they must be joinedat the edge or they will not interlock when a pressure is applied toattempt to interlock them and close the bag.

It is accordingly an important object of the invention to provide amethod and structure for completing reclosable bags which havecontinuous interlocking elements along the top, and wherein the bag isopened, and the interlocking elements are separated after the bag isdelivered to the customer. The same problem occurs and is solved by theinvention where the customer makes the bags on his premises and desiresto have an open bag to fill which does not have to be opened by aseparate operation.

A feature of the invention is to take the continuous supply of bagmaterial having opposing thin plastic film layers with interlockedfacing rib and groove profiles along one edge and to insert a separatingfinger between the rib and groove profiles to separate them. They areseparated, but the rib and groove profiles are maintained in opposingalignment with each other by traveling along in grooves in theseparating finger with the grooves being sufficiently deep so that theyguide the sides of the rib and groove, but do not engage the surfacesfacing each other to in anyway flatten the rib and groove. A furtherfeature of the invention then resides in immediately interlocking andcross-sealing the profile very close to the separating finger end whilethe profiles are maintained in exact alignment, and the profiles arebrought into almost closed position just before joining and sealing sothat the rib and groove elements move a minimum distance to engage andinterlock when struck by the sealer.

Other objects, advantages and features, as well as equivalent methodsand structures which are intended to be covered herein, will become moreapparent with the teaching of the principles of the invention inconnection with the disclosure of the preferred embodiments in thespecification, claims and drawings, in which:

DRAWINGS

FIG. 1 is an end elevational view somewhat schematically shown, oflayers of film being handled in accordance with the method of thepresent invention, and mechanism embodying the principles of theinvention;

FIG. 2 is a fragmentary view of a portion of FIG. 1 illustrating sealingbeing performed;

FIG. 3 is an enlarged fragmentary sectional view taken substantiallyalong line III--III of FIG. 1;

FIG. 4 is an enlarged fragmentary sectional view taken substantiallyalong line IV--IV of FIG. 1;

FIG. 5 is an enlarged fragmentary sectional view taken substantiallyalong line V--V of FIG. 1; and

FIG. 6 is an enlarged fragmentary sectional view taken substantiallyalong line VI--VI of FIG. 1.

DESCRIPTION

As illustrated in FIG. 1, opposed layers of thin film 12 and 10 arebrought forward from a supply in the direction of the arrowed line 11.The thin film layers have on their facing surfaces critically shapedsmall interlocking rib and groove profiles illustrated by a rib 14 and agroove 13. As is customary from the production machine, the material isrolled onto rolls, with the profiles interlocked, and when it is to bemade into bags, it is unrolled off of the rolls.

To open the profiles, the film layers and the interlocked profiles arefed over a separating finger 19. The separating finger has a smoothrounded leading edge 20 which forces the rib and groove profiles toseparate, and the profiles travel into grooves 21 and 22 on the upperand lower surfaces of the finger 19. The separating finger is positionedalong the path of travel of the film layers so that the rib and grooveelements 14 and 13 enter into the grooves in the finger. As illustratedin FIG. 3, the grooves 21 and 22 in the surfaces of the finger 19 have asize so that the outer surfaces of the finger beside the grooves pushupwardly and downwardly on the film, and the groove and rib elements 13and 14 lie in the grooves without touching the bottom. Also, the sidesof the finger grooves are such that they guide the rib and grooveprofiles by engaging them laterally, but not on their facing surfaces,so that they in no way tend to flatten the rib or groove profile.

The finger groove 21 for the groove profile 13 has sides 23 and 24 whichmay just touch the groove profile 13, but the bottom 25 is sufficientlydeep that the lower ends of the groove profile generally do not slideagainst the surface 25.

Similarly, the width of the groove 22 for the rib profile 14 is suchthat the tip of the rib generally does not hit the bottom 22, but thesides 26 and 27 are such that they laterally guide the rib in an uprightposition. The grooves 21 and 22 are positioned on the finger so thatthey maintain the rib and groove profiles exactly opposite each other.

Thus, as the rib and groove pass over the finger and are separated, theywill again approach each other on the offrunning side of the finger. Thefinger is of a thickness so that the rib and groove are separated assmoothly as possible and thereafter the distance between the fingergrooves is reduced to only a fraction of an inch, with the material ofthe finger between the base of the grooves 21 and 22 at the running offside being of sufficient thickness only to give the finger sufficientstrength. To help insure that the rib and groove elements ride in thefinger grooves, pressure or retaining rollers 30 and 32 are positionedopposite each other and similar retaining rollers 31 and 33 arepositioned opposite each other to press the film lightly against thefinger and to keep the profiles into their respective grooves as theyslide therebetween. The finger will have smooth polished outer surfaceswhich may be Teflon coated for easy sliding of the film.

The finger will be tapered to a point at 29 so that the rib and grooveelements 14 and 13 can approach each other while still being guided inthe grooves of the finger. Their relative position is shown on theoffrunning side of the finger in FIG. 4.

As illustrated in FIG. 5, at the time of reaching the sealer, the ribelement 14 should be seated just against the groove element 13, andready to enter between the jaws when sealing bars 42 and 43 pressagainst the outer surfaces of the film to form a cross-seam.

The film material is drawn forward in a suitable way such as by belts 34and 35. The belts are driven by suitable mechanism, not shown, whichdrives them intermittently in coordination with the drive for operatingthe sealing bar 42. This drive is also omitted, but may be ofconventional design, such as a pneumatic cylinder, indicatedschematically by the arrowed line 45. Preferably, the belts maintain aslight tension on the material when not drawing it forward. If desired,the lower sealing bar may be stationary so that only the upper bar movesup and down and carries out the sealing operation. The sealing bars maybe accompanied by a simultaneous cutting as indicated by the knife 44.This knife may completely sever the bag, or may form either a line ofweakened resistance or separated cuts in a dot and dash formation sothat individual bags may be torn off the supply at a later point. As across-seal is being formed by the sealing jaws 42 and 43 movingtogether, the rib element 14 will be pressed directly into the grooveelement 13 so that at the trailing end of the previously sealed bag andthe leading end of the newly formed bag, the rib and groove will be inexact alignment, while at the same time the rib and groove elements willbe in unlocked position along the rest of the bag thereby permittingclosing of the bag after it is filled. As referred to above, this is anessential factor because if the rib and groove are not in alignment andare not sealed together and interlocked at the edges of the bag, the riband groove cannot be interlocked along the bag length. Or, if they arenot interlocked at the end, it is possible that they can be joined inthe center of the bag, but there will be an air leak at the ends wherethe rib and groove do not join.

In operation the film layers are intermittently advanced, and theprofiles are separated by the separating finger a minimum distance, andmaintained in exact alignment. They are guided back together so thatthey are in adjacent relationship before the sealing bar is closed. Ithas been found that the sealing bar must be kept very close to thetrailing tip 29 of the separating finger, and that a distance of nogreater than 1/2 should exist between the place where the sealing barscome together and the trailing end 29 of the separating finger. Thesealing bars are intermittently brought together, and the bars as theyfirst engage the film interlock the rib and groove profiles, and as theycontinue together, they engage the profiles and the film with sufficientpressure to form a seal. Suitable heating elements are embedded in thebars to heat them to a degree to fuse and seam the thermoplastic. Thebars are then separated and a fresh width of bag is moved, and theoperation is repeated to form successive bag widths.

I claim as my invention:
 1. A method of preparing bags of thin plasticfilm having continuous reclosable fasteners comprising thesteps:continuously advancing facing layers of plastic bag film havingfacing interlocked rib and groove profiles on the inner surface adjacentone edge of the layers; positioning a separating finger between the riband groove profiles along the path traveled by the layers so that theprofiles are separated; holding said rib and groove elements in exactopposing alignment while traveling over the separating finger; andimmediately after the separating finger intermittently pressing thelayers together transversely of their length at intervals determined bythe width of the bags desired by pressing together sealing bars at asealing location to press the profiles together into interlockingengagement and applying heat to form cross-seams on the layers.
 2. Amethod of preparing bags of thin plastic film having continuousreclosable fasteners in accordance with the steps of claim 1:includingapplying the pressing step at a location no greater than 1/2 from thelocation of said separating finger.
 3. A method of preparing bags ofthin plastic film having continuous reclosable fasteners in accordancewith the steps of claim 1:including supporting the layers afterseparation by forces against the film laterally of the profiles withoutengagement with the facing portions of the profiles.
 4. A method ofpreparing bags of thin plastic film having continuous reclosablefasteners in accordance with the steps of claim 1:including the step ofbringing the layers toward each other into touching engagementimmediately prior to said step of pressing the layers together.
 5. Amethod of preparing bags of thin plastic film having continuousreclosable fasteners in accordance with the steps of claim 1:includingmaintaining a longitudinal tension on the layers during all of the stepsof the method by applying a pulling force drawing the layers over theseparating finger.
 6. A method of preparing bags of thin plastic filmhaving continuous reclosable fasteners in accordance with the steps ofclaim 1:including the step of simultaneously cutting the layers at thetime of said applying heat and at the location of the cross-seams.